The present invention relates to an improved controller for a videotape recorder (VTR) and, more particularly, to an improved controller for a VTR for use in tape editing and playback.
In the operation of broadcast-type VTRs, it is often desirable to be able to control the VTR and, more particularly, to control remotely the VTR to produce a number of special effects with the recorded program material, such as variable motion effects and post-production editing.
In order to control the VTR and to produce these special effects with the program material, which is recorded on the tape, the controller must selectively advance or rewind the tape on the VTR to a particular frame or frames.
The Society of Motion Picture and Television Engineers (SMPTE) has adopted a standard specifying that a timing code that corresponds to each frame of video information should be recorded on the audio track of the videotape. The timing code of each frame is read by a timing code reader producing a signal which is representative of the time length of the material recorded on the tape. The SMPTE standard further specifies that the timing code should be readable by the timing code reader when the videotape is transported over a wide range of speeds. By reading the timing code, the controller can selectively advance or rewind the tape on the VTR to a particular frame or frames.
In practice, however, the timing code cannot be accurately read by the timing code reader when the tape is transported at low speeds. Thus, control of the VTR cannot be accurately made.
A tachometer, which is connected to the transport mechanism of a VTR for moving the videotape, is well-known in the art. The tachometer generates signal pulses which are representative of the speed at which the tape is being transported. It is also well-known in the art that a tape time reader receives the signals from the tachometer and generates a signal which is representative of the time length of the material recorded on tape.